We have recently completed the interviewing of cases (n = 683) and controls (n = 1653) in a collaborative epidemiologic study of multiple myeloma (RO1 CA 23350). While the original grant did not provide for any resources to further characterize multiple myeloma (MM) cases according to immunoglobulin type and other parameters of their disease that might be indicative of etiologic heterogeneity, we were able to obtain these data on 43% of cases. Data from other studies and our preliminary analysis suggest that the separation of MM cases based on immunoglobulin type, in particular, could prove important, and that failure to examine cases according to immunoglobulin type could reduce the sensitivity of the investigation. Thus, this proposal requests funds for the completion of: (a) the ascertainment of clinical and laboratory data on the MM cases; and (b) the analysis that incorporates these data with those already obtained through interviews.